Investigation to show how the amount of electric current affects the amount of copper deposited at the electrodes during the electrolysis of copper sulphate solution using copper electrodes.

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Introduction

Investigation to show how the amount of electric current affects the amount of copper deposited at the electrodes during the electrolysis of copper sulphate solution using copper electrodes by Mohammed Bakir Aim: I aim to investigate how the amount of electrical current affects the amount of copper deposited in the electrolysis of copper sulphate solution using copper electrodes. Hypothesis: Electrolysis is the decomposition of a molten or aqueous compound by electricity. The compound decomposed during electrolysis is called an electrolyte. The energy which causes the chemical changes during electrolysis is provided by an electric current. It is important to remember that an electric current is simply a flow of electrons. When an electric current passes through the electrolyte, electrolysis takes place. During electrolysis: * a metal or hydrogen forms at the negative cathode. This confirms that metals and hydrogen have positive ions. These ions are called cations because they are attracted to the cathode. * a non-metal (except hydrogen) forms at the positive anode. This confirms that non-metals (except hydrogen) have negative ions. These ions are called anions because they are attracted to the anode. The experiment which I am to carry out involves an electrolyte of copper sulphate solution and electrodes made of pure copper. I am to investigate how the amount of electric current affects the amount of copper deposited at the electrodes during the electrolysis of the copper sulphate solution using the copper electrodes. I have already explained that the copper will form at the negative cathode as metals have positive ions. When an electric supply is connected to the electrolytic cell, electrons flow from the anode to the battery and from the battery to the cathode. This is why the anode is positive as electrons have been drawn from it, and why the cathode is negative as electrons are given to it. As the electrolyte is of course an ionic compound, it contains positive and negative ions. ...read more.

Middle

My experiment is also a good way of carrying out the investigation because it will allow me to gain enough accurate and reliable results over a good range to allow me to test my hypothesis and draw valid conclusions. Before conducting my final experiment I arranged to conduct a trial experiment. This trial experiment was intended to familiarise me with the experiment before I did the final one and also to help me improve the method I was working on and to guide me on the best way to conduct the actual experiment. In the trial experiment I tested my method and ameliorated it, correcting any mistakes and building on any faulty points. It caused me to think about the surface area of the electrodes immersed in the electrolyte and how it was important to control in order to ensure that my experiment was a fair test. It also helped me to decide on the time I would leave the experiment as I found that 2mins is sufficient time for electrolysis to occur and for enough to happen so that I could draw valid conclusions. Apart from improving my method, the trial experiment also gave me confidence in my hypothesis and in what I was doing. It also helped me to set-up and conduct the final experiment as quickly as possible, thus making it possible for me to repeat the experiment 4 times. Results: Here are the results for my experiment along with the changes in mass after electrolysis has taken place: Current (amps) Anode Before (grams) Anode After (grams) Change in Mass (grams) Cathode Before (grams) Cathode After (grams) Change in Mass (grams) 0.2 1.37 1.34 -0.03 2.09 2.14 0.05 0.2 1.34 1.30 -0.04 2.14 2.17 0.03 0.2 1.30 1.27 -0.03 2.17 2.21 0.04 0.2 1.27 1.22 -0.05 2.21 2.25 0.04 0.4 1.22 1.14 -0.08 2.25 2.33 0.08 0.4 1.14 1.07 -0.07 2.33 2.42 0.09 0.4 1.07 1.01 -0.06 2.42 2.49 0.07 0.4 2.74 2.60 -0.07 1.31 1.38 0.07 0.6 2.60 2.51 -0.09 ...read more.

Conclusion

Instead my experiment took me three lessons to complete. This change of electrodes would have affected their surface areas which would in turn affect the rate of electrolysis. This problem could have been overcome if I had continued to conduct my experiment or if I had taken or reserved the electrodes that I had been using for my experiment. Another problem with my experiment was that I had to adjust the current with the rheostat while electrolysis was taking place. This meant that at first the current was lower than it should be and then it was adjusted. This could have produced some inaccuracies in my results. It would be more accurate to prepare the rheostat beforehand and thus have it ready on the precise current. Another inaccuracy was the water and propanone I used to clean the copper electrodes with. Because of the many experiments taking place and because many people had cleaned their electrodes so many times, the distilled water and propanone had become contaminated with copper sulphate solution which could be seen as both the distilled water and propanone had a blue tinge to them. This meant that some copper sulphate solution was still on my copper electrodes when I was drying them. This could have caused some inaccuracies in the weight of the copper electrodes but the difference would have been so minute, it could not have been detected on the weighing machine. I could solve this problem by changing the water and propanone each time. However, this would be extremely wasteful and quite unnecessary. There are some further methods that I could carry out in order to provide more evidence for my conclusions. I could, for example, use a different metal and a different electrolyte to see whether the same thing happens with any metal. I could, for example, have used silver electrodes and silver nitrate solution as my electrolyte. This would have further proven my hypothesis and provided me with more evidence with which I could draw general conclusions for all metals. ...read more.

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The atoms will also have a greater charge, which will give them a greater attraction to the cathode causing the electroplating to happen faster. I also predict that the relationship will be directly proportional between the time the voltage and the mass of Copper deposited on the Cathode (negative electrode).

Charge is the number of electrons. If there are twice as many electrons available then twice as many ions can pick up electrons each second. The concentration of the solution does have a significant effect, since the concentration of ions do not make it any easier for the electrons to flow, nor does it affect any

> Turn on the gas and light the Bunsen burner. > Weight the set amount of the carbonate I am testing. > Place it in the test tube. > Put the test tube in the clamp. > Fill the bowl 3/4 of the way up with water.

Auto rip (resistor)- this will be used to change the current going through the circuit. (5) Power pack- this will be where the power comes from and also the current can be changed. (6) Copper sulphate solution- this will be used as the electrolyte (7)

Therefore, in a higher concentrated solution, there is more electroplating. 6). Temperature- Temperature can give more energy to the copper to move. When the temperature is higher, there is more energy available for the copper ions to move from the anode to the cathode.

The electrodes will be kept the same distance apart throughout the whole experiment. Resistance in the wire / ammeter The resistance change could change the current measured. The ammeter will always be kept the same, but the wires will have to be changed in between experiments.

negative electrode - The cathode - and the metal ions would be attracted to the positive electrode - The anode. For this reason we call the metal ions "cations" (from 'Cathode') and the non-metal ions "anions" (from 'Anode'). We know that the amount of electricity in the circuit affects the